The story is introduced by a supposed narrator certify the authenticity. Presented as the nephew of John Carter, it is called emergency in New York and on his arrival, he learns that John Carter was found dead in the morning. In his will, John Carter asks to be buried in a mausoleum opening only from the inside. He left behind a manuscript that will form the heart of the story.
In it, John Carter tells what happened to him years ago when he was looking for gold in Arizona with a partner. Attacked by Apaches, his friend is killed and he finds refuge in a mysterious cave where he was seized with a sudden numbness. While the Apaches are visibly terrified by what there is in the cave, John Carter is literally torn from his body and finds himself split, standing naked beside his own body. Then attracted by Mars shining in the sky, the planet that has always fascinated, he reaches out to her and feels transported through the void.
John Carter wakes up naked on the floor of the red planet where he soon discovers that he is able to make huge leaps because of the low gravity, allowing it to escape a band of green Martians who attack to protect the enclosure where their young are. This physical feat is to be captured rather than killed him.
Green Martians who captured are creatures of more than four meters, with two legs, two arms and two intermediate members can serve as legs or hands. They live in herds that occupy old abandoned cities, apparently built by human beings size living rapine and are continually at war. They are cruel and brutal beings rapidly conceive of respect for John Carter, especially when one of them kills with a single punch, thus taking the property and the title of the death. Both prisoner and leader John Carter is guarded by the Martian equivalent of a dog, Woola, a cap which he went quickly master in saving his life while he earns the respect of Tars Tarkas, a noble Thark (the tribe of green Martians where he lives), which seems less brutal than other green Martians.
